1. Field of the Invention
The present invention generally relates to a paint booth construction. More particularly, the present invention relates to a paint booth arrangement and method for directing airflow through the paint booth for maximizing floor space and operational efficiency.
2. Brief Description of the Prior Art
Paint booths are used to enclose certain dangerous activities that are performed therein (such as painting and stripping) and to contain the risk of fire. Paint booths are further utilized to control the overspray from the spray paint guns and capture the paint particles that are not applied to the object being painted. Paint booths are designed in accordance with local and national electrical and fire codes and are usually surrounded with single or double skinned walls. Some of the more pertinent prior art relating to paint/spray booths and the like are briefly described hereinafter.
U.S. Pat. No. 4,515,072 ('072 Patent), which issued to Crisp, discloses a Spray Booth. The '072 Patent teaches a spray booth for use in spray painting motor vehicles, which booth comprises an air supply duct that extends centrally along the length of the top of the booth and has an air supply opening fitted with a cloth filter in its underside. The opening extends from near one end of the booth right up to the outer end and is supplied with air by a fan from the one end of the booth. A single air outlet opening is provided at the middle of the bottom of the one end of the booth and is connected to an air extraction fan. The velocity head of the air flow from the air supply fan decreases along the length of the air supply opening from the one end to the other and accordingly the pressure head increases so that the downward air flow from the filter cloth per unit length of the air supply opening decreases from the one end to the other end of the booth. This arrangement achieves an extremely efficient downward air flow pattern in the booth with little or no turbulence so that, after spraying, droplets of paint with which the air in the booth is contaminated after spraying are not precipitated on the surface which has been sprayed.
U.S. Pat. No. 5,095,811 ('811 Patent), which issued to Shutic et al., discloses an Automotive Powder Coating Booth with Modulated Air Flow. The '811 Patent teaches a method and apparatus of powder coating relatively large objects such as automotive or other vehicle bodies. The apparatus comprises a spray booth having an interior comprising a cut-in coating zone having a relatively large area to permit the application of powder onto the interior portions of the vehicle body such as the inner door flanges, a side coating zone area wherein the vertically oriented, exterior surfaces of the vehicle body are coated such as the doors and fenders, an overhead coating zone in which the horizontally oriented, exterior surfaces of the vehicle body are coated such as the hood, roof and trunk, and, two transition zones separating the three coating zones. Air infeed and exhaust devices associated with each coating zone and each transition zone are operated to vary the air flow rate within the booth interior in the course of movement of the vehicle body therethrough such that the air velocity in each coating zone is maintained below a predetermined maximum downdraft velocity throughout the coating operation, and such that a slightly negative pressure is maintained within the booth interior.
U.S. Pat. No. 5,284,518 ('518 Patent), which issued to Kohn, discloses a Recirculation Ventilation System for a Spray Booth. The '518 Patent teaches a spray booth ventilation system adapted for receiving long, slender work pieces suspended from an overhead monorail conveyor. The pieces are carried into and out of this booth, where the paint is applied by conventional equipment. The gases within the booth, which are a mixture of fresh air and evaporated paint solvents, are partially re-circulated and re-injected into the booth at discharge orifices defining the edges of the entrance of the booth. Arrangements are provided for equalizing the flow throughout the booth in a vertical direction to avoid points of stagnation which might cause fumes from the booth to emerge from the opening, so that the velocities of the inflow can be minimized to eliminate the danger of collision of the parts as they swing in response to the gas flow, and thus cause damage to the painted surfaces.
U.S. Pat. No. 5,395,285 ('285 Patent), which issued to Milton, discloses a Dehumidifier (for use in combination with a spray booth). The '285 Patent teaches system to dehumidify a substantially sealed chamber such as a spray chamber, which system comprises a re-circulating duct for re-circulating air within the chamber. The duct includes an exchange aperture facing the direction of flow of air. A fan to draw air through the duct is positioned downstream of the exchange aperture. A heater is provided preferably within the re-circulating duct and preferably located downstream of the display aperture.
U.S. Patent Application No. 2002/0119254, which was authored by Deregge, discloses an Integrated Air Flow Booth (and methodology). The publication describes a spray booth comprising a housing having a ceiling and a set of walls that each has a bottom end and a top end, with the walls and the ceiling defining an interior. An air intake is disposed in the ceiling, and an exhaust outlet is disposed near the bottom end of one the walls. A circulation system is used to introduce air into the interior through the intake and to exhaust air through the outlet. Further, the air intake is configured to produce an airflow gradient within the interior such that the flow rate decreases in a direction toward the outlet and such that the airflow through the interior is in a generally downward direction.
U.S. Patent Application Publication No. 2006/0243202, authored by R. L. Thelen, discloses an Aircraft Spray Booth, which invention is directed to an aircraft spray booth providing for effective removal of particulate matter, overspray and volatile organic compounds from the spray booth area without premature and uneven clogging of the filtration system. The invention is designed to create an accelerated airflow within the plenum of the spray booth to prevent or minimize stratification of the air and reduce particulate matter fallout. The airflow through the booth is increased by the reduction of the spray booth and filter area to approximately ⅓ of the original booth width. The decrease in the cross sectional area of the spray booth increases the overall speed of the airflow and decrease the volume of air exchanged through the booth. The spray booth is tapered at the reduction area to cause acceleration of the air at the sidewalls. The acceleration of air at the sidewalls causes a purging of air along the sidewalls and prevents paint and other particulate matter from adhering to the sidewalls. The reduction in the spray booth allows lighting can be placed closer to the painted surface in the tail and fuselage section of the aircraft to aid in the accuracy of the painting process.
It should thus be understood that paint booths typically comprise a filter section comprising a set of filter racks, a plenum, and a set of filters. The plenum is under a negative pressure caused by a fan, which ejects filtered airflow to the atmosphere. In order to properly clean/filter air to meet certain safety requirements, airflow velocity (speed and direction) in a paint booth is an important consideration. Airflow speed is usually held to be a constant and uniform rate (a common rate being 100 feet per minute) from the intake end of the booth to the exhaust end. In the conventional paint booth design, paint booth cross sectional area is constant from entrance to exhaust.
There are essentially two types of paint booths in the industry, namely so-called cross draft booths and downdraft booths. In cross draft booths the airflow is generally horizontal. In downdraft booths the airflow moves from the ceiling to a filter installed in the floor of the booth. Both types of paint booths are in common use in the industry.
Intake air to conventional paint booths typically arrives in one of two ways, namely a draw through style paint booth or a forced air style paint booth. In a draw-through style paint booth, intake air may be admitted to the painting environment through the open front of the booth or intake air may be admitted to the painting environment through a filtered door or doors consisting of door frames equipped with filter racks and filters in lieu of solid walls. The filter door style has the advantage of controlling the cleanliness of the air entering the booth. The open front style is only used where cleanliness is of moderate concern.
In the forced air style of paint booth, the intake air is forced into the booth through an intake air chamber consisting of a filter chamber, filter racks and filters. The advantage of this latter style of air intake is that the air may be pre-cleaned in the fan unit with one or two stages of filters and then cleaned once again at the intake chamber. This style assures the painter of best possible cleanliness of air entering his paint booth.
Paint booths are usually equipped with a fire protection system that may be dry chemical, foam or water based or a combination thereof. Paint booths must then be designed to support the piping for the fire protection system as well as the rest of the enclosure itself. Structural design is as important as any other phase of design including lighting and filtration and air moving.